As is well known, slab formwork systems are systems meant for formworks of large horizontal surfaces where a high performance and high surface finish are required. They consist basically of a structure comprised of vertical braces, support bolsters provided on the upper end of the braces, and longitudinal beams mounted on the support bolsters, occasionally including cross beams, and completed by the wooden boards that define the formwork skin placed over the longitudinal or primary beams. Currently, wooden boards are often replaced with formwork panels comprised of a frame and a number of internal reinforcement partitions that support the formwork surface or skin, said formwork panels defining modular elements that simply rest on the beams without requiring nailing.
Support bolsters are meant to allow recovering part of the formwork before the concrete sets fully, allowing to reuse the materials recovered for following formworks.
Said support bolsters are generally comprised of a support surface that is in contact with the concrete and support and coupling means for the beams, with the latter means vertically moveable and capable of assuming two positions, an upper working position and a lower stripping position, such that in order to pass from one position to the other the bolsters are provided with the corresponding locking and release systems that allow the bolster to slide with respect of the brace to pass from the upper to the lower position; thus, in the latter position the beams and formwork panels also descend, allowing them to be recovered and reused for the following formwork.
Likewise, currently being used are formwork systems known as “grids” characterised in that the formwork panels are always in a given position on the beams, that is, the panels do not rest astride two consecutive beams, as is the case in “row” formworks, but instead have end panels reaching the end of the beam, that is, exactly as far as the following braces. These grid formwork systems are further complemented by flashing profiles placed transversally to close any spaces left between panels supported by a pair of longitudinal or primary beams and those of the following grid. In the stripping operation the longitudinal or primary beams and the panels are removed, and the braces and flashing profiles are left in place as these are generally between the concrete and the braces themselves.
In this sense, examples of slab formwork systems with support bolsters are those corresponding to British Patent 2,005,332 by Rapid Metal Developments Limited; German Patent 3316557 and German Utility Model G9005901 by Noe Schaltechnik GmbH.; Spanish Patent 440,081 by SGB GROUP LIMITED; European Patent 0718453 and French Patent 2,475,099 by Peri GmbH.
The slab formwork systems with support bolsters described in the aforementioned documents have drawbacks such as a slow and complex assembly of the formwork, as a beam is first mounted on its two corresponding braces and then the other beam of the grid is mounted also on its two corresponding braces, placed parallel to the first, calculating the separation between the two beams in an approximate manner to then place between them the various formwork panels that will finally determine the exact separation between the beams. This means that assembling the panels implies a readjustment of the positions of the beams and braces, which generally requires at least two workers, one placing the panels and the other moving the braces and beams as necessary, or instead assembling the beam and brace structure with a great precision of measurements and positions.
In any event, the structure consisting only of beams and braces is not sufficiently rigid, so that it is best to simultaneously assemble the beams that form the grid and the braces, thereby requiring more than one worker and a greater assembly time as the person assembling the panels must wait until the braces and beams have been raised, which generally requires more time. In addition, and especially when the formwork is at a great height, the panels are mounted from the top and the braces and beams from the floor, so that it would be very difficult for a single worker to assemble the entire formwork, as this would require constantly travelling up and down.